Double wall fittings for use with double wall pipeline systems

ABSTRACT

A double wall compression fitting is dimensioned for attachment to a double wall pipeline system having an inner pipeline and an outer pipeline. The fitting is comprised of an inner housing having at least two terminals, an outer housing encasing the inner housing in a manner to form an annular space therebetween and a compression connecting assembly. The compression connection assembly connects the inner and outer housings to the double wall pipeline system so that the annular space between the housings is in communication with an annular space between the pipelines of the double wall pipeline system. The compression connecting assembly includes a coupler with means to compress it to form a compression seal with the outer pipeline, and a compression spacer with at least one lateral communication port.

This is a continuation-in-part of Ser. No. 07/680,513, filed Apr. 4,1991, "Double Wall Fittings For Use With Double Wall Pipeline Systems"now abandoned.

This invention relate to fittings for use on pipeline systems forconveying liquids. More particularly, the invention relates to doublewalled fittings for use on double wall pipeline systems.

BACKGROUND OF THE INVENTION

Pipelines are used extensively for conveying liquids. One area wherepipelines are used is in the transporting of liquid from bulk storagetanks. Many types of liquids are stored in bulk, both above ground andunderground. A special problem exists with leaks in the pipelines usedin connection with underground storage tanks. If the liquid beingconveyed is a danger to the environment or the health when notcontrolled, substantial damage can occur before the leak is evendetected. A good example of this are the pipelines used to convey liquidgasoline at retail gasoline service stations. Necessarily, thesestations are in populated areas and therefore there is always a dangerassociated with leaks from the tanks or pipelines associated therewith.

Leaked gasoline poses a hazard to the environment as well as an obvioushealth hazard. Any leak which develops is normally very slow initially.This means that the leak is difficult to detect until a substantialamount of gasoline has leaked. By that time environmental damage andpossible health problems have occurred.

Various attempts have been made to alleviate the problems associatedwith underground pipelines, including use of double walled pipelinesystems. In this type of system, an outer pipeline wall acts as acontainment vessel if an inner pipeline wall develops a leak. A slowleak in the pipeline is satisfactorily contained. However, installationof known double walled pipelines is difficult. Initially there can be aproblem of getting the inner pipeline inside of the outer pipeline. Thisis especially true for long lengths of pipelines wherein the innerpipeline is flexible. Even a semi-rigid inner pipeline is difficult towork with due to the fact it is normally wound on a reel inmanufacturing. The curved nature of the pipeline stored and shipped inthis manner tends to persist.

Another problem experienced with double wall pipeline systems is theneed for special fittings normally needed with any pipeline system.Straight fittings, elbows and T-fittings are often used in connecting apipeline terminal to another pipeline terminal, dispenser, etc. Knownfittings used on conventional single wall pipelines are not able tomaintain a segregation of the inner pipeline flow channel from the outerpipeline flow channel. The lack of reliable easy to use fittings for useon double wall pipeline systems has reduced the attractiveness of suchsystems.

There has now been discovered double wall fittings for double wallpipeline systems. The fittings solve many of the problems inherent withthe existing fitting systems. The fittings of this invention areeconomical and provide a means of connecting not available previously.

SUMMARY OF THE INVENTION

A double wall compression fitting is dimensioned for attachment to adouble wall pipeline system having an inner pipeline and an outerpipeline. The fitting is comprised of an inner housing having at leasttwo terminals, an outer housing encasing the inner housing in a mannerto form an annular space therebetween and a compression connectingassembly. The connection assembly is capable of connecting the inner andouter housings to the double wall pipeline system so that an annularspace between the housings is in communication with an annular spacebetween the inner and outer pipelines of the double wall pipelinesystem. The compression connecting assembly has a coupler with means toform a compression seal with the outer pipeline and to compress acompression spacer so as to transmit an inward compressing force to theinner pipeline. The compression spacer is characterized in having ameans of communication between the annular space of the double wallpipeline system and the annular space between the housings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view in section of a double wall fitting of theinvention.

FIG. 2 is a side view in section of another double wall fitting of theinvention.

FIG. 3 is a side view in section of still another double wall fitting ofthe invention.

FIG. 4 is a perspective view of a double wall pipeline system with asection of a compression spacer forming a part of the fitting of FIG. 1removed therefrom to show its operation.

FIG. 5 is a view in perspective view of a double wall pipeline systemwith a section of a compression spacer forming a part of the fitting ofFIG. 3 removed therefrom to show its operation.

FIG. 6 is a side view in section of an elbow double wall fitting with acoupler assembly.

FIG. 7 is a side view of a double wall fitting having a means formonitoring an annular space between housings.

DETAILED DESCRIPTION OF THE INVENTION

The double wall compression fittings of the invention are useful withdouble wall pipeline systems. The fittings depicted in FIGS. 1-3 areT-fittings having three terminals, each connected to a double wallpipeline system. Other fittings such as two terminal straight fittings,i.e. couplers, two terminal elbow fittings and four terminal crossfittings are within the scope of the invention and readily adapted fromthe disclosure of the T-fittings which follow.

With reference to FIG. 1, there is shown a double wall compressionfitting 10 having three terminals. The fitting 10 is used to connectthree separate double wall pipeline systems 11. The pipeline systems 11each have an inner pipeline 12 for conveying a liquid and an outerpipeline 13 encasing the inner pipeline for containing any leakedliquid. An annular space 14 is formed between the pipelines. The doublewall pipeline systems 11 are made of an extruded plastic. Other rigidand semi-rigid materials can as well be used to form the pipelinesystems. The inner pipeline generally ranges from about one-half inch toabout six inches in diameter and the outer pipeline slightly larger,though the diameters of the pipelines are not critical and are dictatedby the end use.

In accord with this invention, the fitting used for the double wallpipeline systems 11 ensures that the flow paths of liquid in the innerpipeline remains separate when passing through the fitting. Thus, eachinner pipeline is connected to the fitting in a sealed manner so thatliquid which flows through one inner pipeline will be forced to flowinto one or more other inner pipelines. Similarly, a common separatepath connects the annular spaces 14 between the three pipelines.

The double wall compression fitting 10 is comprised of an inner housing15, an outer housing 16 substantially encasing the inner housing and acompression connecting assembly 17. Each of the components is describedin detail below.

The inner housing 15 is preferably a one piece construction. Theinterior of it forms a flow path connecting the flow of liquid throughthe inner pipelines of the double wall pipeline systems. Each leg of theinner housing has an externally recessed terminal 18, preferably with aseries of ridges 19 extending around its circumference to better engagethe inner pipeline and retain it when placed thereover. Preferably,though not necessary, O-rings 20 are positioned on the recessedterminals in O-ring grooves 21 to provide a seal with the innerpipeline. Band clamps 22 are also provided to compress the innerpipeline and O-rings onto the inner housing terminals to ensure a liquidtight seal. Preferably, also, a metal reinforcing sleeve 23 is insertedin the terminals of the inner housing to keep them from collapsing.

The outer housing 16 substantially encases the inner housing 15. It hasthe same general shape, though its legs are shorter to allow access tothe band clamps for tightening purposes. A terminal of each leg hasexterior threads 24. An annular space 25 between the housings is formedwhich is in communication with the annular space 14 between the doublewall pipelines through the compression connecting assembly describedbelow.

The compression connecting assembly 17 is used to connect the inner andouter pipelines of the double wall pipeline system 11 to the inner andouter housings of the T-fitting 10 in a sealed fashion while preservingthe integrity of the liquid flow path and the annular space flow path.The compression connecting assembly 17 is comprised of an internallythreaded coupler nut 26 dimensioned to engage the threads on theterminal of the outer housing 16, a gasket bearing retainer 27, acompression seal 28, a ram compression seat 29, a gasket 30 and acompression spacer 31 with communication means such as ports 32. Thecoupler nut 26 has an annular flange 33 extending inwardly at its head.The gasket bearing retainer 27 is a rigid ring with an inside diametersufficiently large to fit over the outer pipeline 13 and further has aright angle leg which extends from the ring portion. The purpose of theretainer 27 is to receive force from the coupler nut when tightened andtransmit it to the compression seal and at the same time confine thecompression seal. A secondary benefit realized from the retainer is thatit prevents the compression seal from binding against the coupler nut.

The compression seal 28 is a compressible ring which also has an insidediameter sufficient to fit over the outer pipeline and an outer diametersufficient to be fit within the coupler nut 26 and gasket bearingretainer 27. The compression seal when compressed forms a seal betweenthe outer pipeline and the connecting assembly of the fitting 10.

The ram compression seat 29 is a rigid elongated sleeve which fitswithin the coupler nut. It has a length sufficient to contact thecompression seal and outer housing end edge when the coupler nut 26 istightened. The ram compression seat 29 and ring gasket 30 seated at thehousing's end edge aid in forming a seal between the outer pipeline andouter housing.

As best seen in FIG. 4, the compression spacer 31 is ring-shaped with aninside diameter sufficient to fit over the inner pipeline and an outerdiameter sufficient to fit within the inside of the outer pipeline. Thecompression spacer 31 is preferably made in substantially equalsections. Three to six substantially equal sections are most preferredfor ease of installing and for providing optimum compression directingforces.

Slots around the periphery of the compression spacer 31 serve ascommunication means between the annular space between the pipelines andthe annular space between the housings. The number of slots andplacement in the spacer are not critical. At least one slot andpreferably four to eight slots are used. While the slots can be providedon the outer periphery of the spacer, they can as well be on the innerperiphery or interior of the spacer.

The compression spacer 31 is positioned between the inner and outerpipelines at their terminals and serves to prevent the pipelines frombeing crushed by compressive forces imparted by the coupler nut 26 andcompression seal 28. It should be understood that crushing of thepipelines could block the annular spaces communication. Tightening ofthe outer coupler nut 26 forces the gasket bearing retainer 27,compression seal 28, ram compression seat 29 and gasket 30 together toform a seal to ensure that the annular space between the pipelines isclosed to the outside. The compression spacer 31 also transmits aninward compressing force to the inner pipeline.

It should be apparent that the fitting 10 is capable of attachment to adouble wall pipeline system in a manner wherein the flow path of theinner pipeline remains the same and segregated and the annular spaceflow path between the pipelines remains the same and segregated. Assuch, liquid is able to flow through the inner pipeline of a double wallpipeline system, through the inner housing of the fitting and thenthrough one or more inner pipelines of other double wall pipelinesystems connected to the fitting. All the while, a continuous annularspace is maintained.

FIG. 2 also shows a double wall T-fitting 40 with a double wall pipelinesystem 11 as above described connected at each of three fittingopenings. The fitting 40 is comprised of T-shaped inner housing 41having externally recessed male terminals 42 with outer ridges 43 nearthe end of each opening for engaging the inner pipeline 12. As shown,the inner pipeline 12 is forced over the ridges 43 of the recessed maleterminal a sufficient distance that it will remain in place. The innerhousing 41 is encased by a T-shaped outer housing 44. An annular space45 exists between the two housings.

A compression connecting assembly 48 is used to secure each double wallpipeline system 11 to the fitting 40 in a liquid tight fashion so thatthe annular space 14 between the pipelines is sealed and incommunication with the annular space 45 of the fitting. The compressionconnecting assembly 48 is comprised of an internally threaded couplernut 49 dimensioned to engage threads on the outside wall of the outerhousing 44, a gasket bearing retainer 50, a compression seal 51, a ramcompression seat 52, a gasket 53 and a compression spacer 54 withlateral communication ports 55. The gasket bearing retainer, compressionseal, ram compression seat and gasket are as described above withrespect to FIG. 1 and perform the same respective functions. Thecompression spacer 54, however, is different to accommodate thedifferent terminals of the pipeline system. Thus, as best seen in FIG.5, the spacer 54 is a ring with an inside diameter substantially equalto the outside diameter of the inner pipeline and an outside diametersubstantially equal to the inside diameter of the outer pipeline 13. Thespacer also has an annular flange 56 extending outwardly from itsperiphery a sufficient distance to be substantially equal with theoutside diameter of the outer pipeline 13. As such, the compressionspacer fits over the inner pipeline. Its flange 56 abuts against the endedge of the outer pipeline and its ring portion fits within the annularspace between the inner and outer pipelines. Lateral slots 55 extendingaround the periphery of the spacer including the flange 56 provides thecommunication ports.

Tightening of the compression connection assembly 48 ensures that theannular space between the pipelines is closed to the outside. Thetightening also compresses the compression spacer 54 inwardly totransmit a compressing force to the inner pipeline and to form a sealbetween the inner pipeline and inner housing.

The annular flange found on the compression spacer of FIG. 2 isparticularly desirable in that it aids the mechanic in the field to knowif the components of the fitting are properly positioned beforetightening of the coupler. The annular flange also helps to preventpipeline creep when the fitting and the double wall pipeline areassembled and in use. It should be apparent that other compressionspacers configured to have an annular flange are also possible. Theflange can extend inwardly only and outwardly only. All threeembodiments provide the anti-creep benefit. It should be understood thatmodifications to the pipeline terminals are needed to accommodate theparticular compression spacer.

The double wall compression fitting of FIG. 3 illustrates an embodimentof the invention having still another means of forming a seal between aninner pipeline of a double wall pipeline system and a fitting. Thefitting 60 comprises a T-shaped inner housing 61 with a T-shaped outerhousing 62 wherein the terminals of the outer housing extend past theterminals of the inner housing. A T-shaped sleeve 63 is encased in theinner housing with its legs extending therefrom. Each leg has a flaredend 64 over which the inner pipeline 12 of the double wall pipelinesystem 11 is forced. The outer housing 62 has an internally recessedmale terminal 65 on each end substantially opposite the end of theprotruding sleeve 63 extending from the inner housing 61 for purposesdiscussed below. The outer housing also has external threads 67 on eachterminal.

The double wall pipeline systems 11 are attached to the inner and outerhousings of the fitting 60 by means of a compression connecting assembly68. The assembly comprises an internally threaded coupler nut 69, agasket bearing retainer 70, a compression seal 71 and a compressionspacer 72 with lateral communication ports 73. The components coincidein their form and function with compression connecting assemblycomponents described above with reference to FIG. 2. However, theassembly of FIG. 3 does not require a ram compression seat and gasketdue to the particular configuration of the housings. Thus, thecompression seal 71 of the fitting 60 is able to form a seal with theouter housing 62 by being forced by the coupler nut into direct contactwith the housing's interior wall at or near a terminal.

Tightening of the coupler nut 69 of the compression connecting assembly68 compresses the compression seal 71 directly against the outer housingend wall while also compressing the compression spacer 72 against theend wall of the inner housing 61 and the metal sleeve 63. The combinedactions ensure that the liquid flow path channel of the inner pipelinesand the annular flow path channel between the inner and outer pipelinesremains separate, i.e. they are sealed as they pass through the fitting60.

An elbow fitting with another compression connecting assembly isillustrated in FIG. 6. The double wall compression fitting 80 comprisesright angle elbow inner housing 81 with an outer housing 82 encasing it.A metal sleeve 83 is positioned in each terminal of the inner housing 81to keep the terminals from crushing from the compression connectingassemblies 84 during use. The inner housing has externally recessed maleterminals 85 with ridges 86 extending therearound for enhanced pipelineretention. A set of O-rings 87 positioned in the O-ring grooves 88 onthe male terminal 85 aid in obtaining a liquid tight seal. Optional bandclamps 89 on the inner pipeline 12 terminals provide additional sealingwhen tightened.

The compression connecting assembly 84 is comprised of a coupler 91,band clamps 94 and 95 and a compression spacer 96. The coupler 91 has aninside diameter which allows it to fit over the outer pipeline 13 and anannular flange 92 with an inside diameter which allows it to fit overthe outer housing 82 of the double wall fitting 80. The inside wall ofthe flange 92 abuts against the end wall of the outer housing 82.

When the compression connecting assembly is properly positioned on theouter pipeline 13 and outer housing 82, the band clamps are tightened toform a compression seal between the coupler and the outer pipeline andouter housing. A compression spacer 96 of the type used with the doublewall fitting of FIG. 1 is compressed to aid in forming a seal betweenthe inner pipeline 12 and the inner housing 81. Communication ports 97in the spacer maintain communication between the annular space 14between the pipelines and the annular space 90 between the housings.

The fitting 80 is especially easy to install on a double wall pipelinesystem. It requires a minimum of components. Its ease of installationand reliability make it attractive when economics dictate a lessexpensive fitting.

FIG. 7 illustrates a fitting of the invention having means to monitor anannular space between inner and outer housings of a fitting of theinvention to detect pipeline leakage. The fitting 100 is essentially theT-fitting of FIG. 1 modified to have a detection port instead of a thirdpipeline terminal. The fitting is essentially a two terminal straightcoupler. The fitting 100 has an inner housing 101, an outer housing 102,compression connecting assemblies 103 and a detection access port 104.The inner housing is a straight tube with externally recessed maleterminals 105 at each end. Exterior ridges 106 are provided on theterminals to engage a pipeline and retain it in place. A metal sleeve107 is positioned in each terminal to reinforce the inner housingagainst crushing when the compression connecting assemblies 103 aretightened. The outer housing 102 is T-shaped with each leg havingexternal threads. Two legs 108 and 109 overlie the terminals of theinner housing while a third leg 110 accommodates the detection accessport 104. The inner and outer housings have an annular space 111therebetween.

The double wall pipeline systems 11 are connected to legs 108 and 109 ofthe fitting 100 by means of the compression connecting assemblies 103.The assemblies and their mode of operation are the same as describedabove with reference to the double wall fitting of FIG. 1. Whenconnected, the liquid flow channel of the inner pipeline 12 is directedthrough the inner housing 101 and through another inner pipeline 12.Similarly, the annular space 14 between the inner and outer pipeline isin communication with the annular space 111 between the housings. Theflow paths are sealed and remain separate due to the unique fitting 100,including its compression connecting assemblies 103.

The detection access port 104 communicates with the annular space 111between the housings. The leg 110 is provided with external threads 112and a coupler nut 113 to hold in place an access line 114. The accessline 114 leads to a detection means (not shown). In this embodiment ofthe invention, the annular space 14 between the pipelines is monitoredto determine any leakage in either pipeline. When not in use, thedetection access port can be closed with a cap nut.

It should be understood that all manners of fittings needed in thesingle wall piping industry are now available in the double wall pipingindustry. Most importantly, the separate flow paths provided by thedouble wall pipelines and their advantages are retained and continuedthrough use of the double wall fittings of this invention.

While the invention has been described with particular reference to thedrawings, other variations and obvious modifications of the describedsystem are considered within the scope of the invention. For example,all manners of attachment means can be used to seal the inner pipelinesto the inner housings of the fitting including the disclosed O-rings,band clamps and ridges as well as adhesives, threads, etc. Also, allmanners of double wall pipelines can as well be used with readyadaptation of the disclosed fittings to the particular pipelinematerials of construction and terminal configurations. All such obviousmodifications are considered within the coverage of the appended claims.

What is claimed is:
 1. A double wall compression fitting for attachmentto a double wall pipeline system having an inner pipeline with terminalsfor conveying a liquid and an outer pipeline with terminals forcontaining liquid with an annular space between the pipelines whereinthe fitting is capable of continuing the functions of the inner pipelineand outer pipeline by connecting to the double wall pipeline system in amanner such that a sealed connection is made with the inner pipeline anda sealed connection is made with the outer pipeline and the annularspace between the pipelines is in communication with an annular space inthe fitting, said double wall compression fitting, comprising:a) aninner housing having at least two terminals; b) an outer housing of thesame general shape as the inner housing substantially encasing the innerhousing in a manner such that an annular space between the housings isformed, said outer housing having at least two terminals; and c) acompression connecting assembly to engage the terminals of the innerpipeline and the terminals of the outer pipeline to the terminals of theinner and outer housings, said assembly having:i) a coupler with meansto compress the coupler to form a seal with the outer pipeline; and ii)a compression spacer positioned between the inner and outer pipelines toprevent said pipelines from being crushed by compressive forces impartedby the coupler and to transmit an inward compressing force to the innerpipeline, further wherein the compression spacer has a means ofcommunication between the annular space of the double wall pipelinesystem and the annular space between the housings.
 2. The double wallcompression fitting of claim 1 wherein the terminals of the innerhousing are externally recessed and extend a sufficient distance beyondthe terminals of the outer housing to accommodate band clamps around theinner housing terminals to secure the inner pipeline of the double wallpipeline system thereto.
 3. The double wall compression fitting of claim2 further comprising at least one O-ring positioned on each of theexternally recessed terminals of the inner housing to ensure a sealedconnection between each said terminal and each of the inner pipelines.4. The double wall compression fitting of claim 3 wherein a band clampis used to compress the coupler to the outer pipeline.
 5. The doublewall compression fitting of claim 3 wherein the outer housing hasexternally threaded terminals, the coupler is a coupler nut withmatching internal threads and further having a compression sealpositioned within the coupler nut to make sealing contact with the outerpipeline upon tightening of the coupler nut.
 6. The double wallcompression fitting of claim 5 wherein the compression seal is acompressible annular ring having an inside diameter sufficient to fitover the outer pipeline and an outside diameter sufficient to fit withinthe coupler nut whereinupon a compressive force from the coupler nutcauses the compression seal to make sealing contact with the outerpipeline.
 7. The double wall compression fitting of claim 5 wherein thecompression connecting assembly further comprises a gasket bearingretainer positioned within the coupler nut, said gasket bearing retainerbeing a ring which fits over the outer pipeline and in contact with thecompression seal to absorb force from the coupler nut and transmit it tothe compression seal.
 8. The double wall compression fitting of claim 5wherein the compression connecting assembly further comprises a ramcompression seat and a gasket in contact with the compression seal sothat upon tightening of the coupler nut, the compression seal is forcedto engage the ram compression seat and gasket to form a seal.
 9. Thedouble wall compression fitting of claim 1 wherein the compressionspacer is an annular ring with an inside diameter sufficient to fit overthe inner pipeline and an outside diameter sufficient to fit within theouter pipeline.
 10. The double wall compression fitting of claim 1wherein the compression spacer is a ring with an annular flange whereinthe ring has an inside diameter sufficient to fit over the outside ofthe inner pipeline and an outside diameter sufficient to fit within theouter pipeline and the annular flange extends from the ring and abutsagainst an end edge of at least one pipeline.
 11. The double wallcompression fitting of claim 1 further wherein the inner housing has ametal sleeve in at least an end to resist crushing when a compressiveforce is exerted thereon.
 12. The double wall compression fitting ofclaim 11 wherein each end of the metal sleeve has a flared enddimensioned to hold the inner pipeline in a sealed fashion.
 13. Thedouble wall compression fitting of claim 1 wherein a detection accessport is provided in the outer housing so that access is gained to theannular space between the housings.
 14. The double wall compressionfitting of claim 1 wherein the compression spacer has at least onelateral port extending therethrough as the means of communicationbetween the annular spaces.
 15. The double wall compression fitting ofclaim 14 wherein the compression spacer has three to six substantiallyequal sections for providing optimum compression directing forces.
 16. Adouble wall compression fitting for attachment to a double wall pipelinesystem having an inner pipeline with terminals for conveying a liquidand an outer pipeline with terminals for containing liquid with anannular space between the pipelines wherein the fitting is capable ofcontinuing the functions of the inner pipeline and outer pipeline byconnecting to the double wall pipeline system in a manner such that asealed connection is made with the inner pipeline and a sealedconnection is made with the outer pipeline and the annular space betweenthe pipelines is in communication with an annular space in the fitting,said double wall compression fitting, comprising:a) an inner housinghaving at least two terminals, wherein said terminals are externallyrecessed and extend a sufficient distance beyond the terminals of anouter housing to accommodate band clamps around said inner housingterminals to secure the inner pipeline of the double wall pipelinesystem thereto; b) an outer housing substantially encasing the innerhousing in a manner such that an annular space between the housings isformed, said outer housing having at least two terminals; and c) acompression connecting assembly to engage the terminals of the innerpipeline and the terminals of the outer pipeline to the terminals of theinner and outer housings, said assembly having:a coupler with means tocompress the coupler to form a seal with the outer pipeline; and ii) acompression spacer to make contact with the exterior wall of the innerpipeline and to prevent said pipelines from being crushed by compressiveforces imparted by the coupler, further wherein the compression spacerhas a means of communication between the annular space of the doublewall pipeline system and the annular space between the housings.
 17. Thedouble wall compression fitting of claim 16 wherein a band clamp is usedto compress the coupler to the outer pipeline.
 18. The double wallcompression fitting of claim 16 wherein the outer housing has externallythreaded terminals, the coupler is a coupler nut with matching internalthreads and further having a compression seal positioned within thecoupler nut to make sealing contact with the outer pipeline upontightening of the coupler nut.
 19. The double wall compression fittingof claim 18 wherein the compression seal is a compressible annular ringhaving an inside diameter sufficient to fit over the outer pipeline andan outside diameter sufficient to fit within the coupler nut whereinupon a compressive force from the coupler nut causes the compressionseal to make sealing contact with the outer pipeline.
 20. The doublewall compression fitting of claim 18 wherein the compression connectingassembly further comprises a gasket bearing retainer positioned withinthe coupler nut, said gasket bearing retainer being a ring which fitsover the outer pipeline and in contact with the compression seal toabsorb force from the coupler nut and transmit it to the compressionseal.
 21. The double wall compression fitting of claim 18 wherein thecompression connecting assembly further comprises a ram compression seatand a gasket in contact with the compression seal so that upontightening of the coupler nut, the compression seal is forced to engagethe ram compression seat and gasket to form a seal.
 22. The double wallcompression fitting of claim 16 wherein the compression spacer is anannular ring with an inside diameter sufficient to fit over the innerpipeline and an outside diameter sufficient to fit within the outerpipeline.
 23. The double wall compression fitting of claim 16 whereinthe compression spacer is a ring with an annular flange wherein the ringhas an inside diameter sufficient to fit over the outside of the innerpipeline and an outside diameter sufficient to fit within the outerpipeline and the annular flange extends outwardly from the ring asufficient distance to abut against an end edge of at least onepipeline.
 24. The double wall compression fitting of claim 16 whereinthe compression spacer has at least one lateral port extendingtherethrough as the means of communication between the annular spaces.